I think the reason the OP got the responses they got was because they did not stop with their complaint about the hotels not honoring their request, but continued with the unnecessary (IMHO) add-on:

"Why these hotels always carry feather pillows? alliance between hotel and chick farm? Cost serving (I doubt that feather is cheaper than polyester)? Political reason (certain states who raise chickens want to protect chicken farmer)?"

when the obvious reason is that it's because other customers (who aren't allergic) prefer them, and the Marriott hotel program wants to satisfy those customers.

I agree that the OP should get better treatment from the hotels for their allergy. But obviously whatever the request is, not all hotels are good about honoring the request.

So with that in mind, maybe the best solution is not to request non-feather pillows at hotel chains that carry feather pillows, but to move to hotel chains that don't carry feather pillows at all. Unfortunately, that presumably means abandoning Marriott Bonvoy.